Enhanced uplink (EU) is one of the major features in third generation partnership project (3GPP) frequency division duplex (FDD) systems. EU offers a peak data rate of 5.76 Mbps. In order to support EU operation, several downlink physical channels are provided to transmit control information. One of the downlink physical channels is the E-RGCH.
FIG. 1 is a block diagram of a conventional wireless communication system 100 which supports EU. The system 100 comprises a wireless transmit/receive unit (WTRU) 102, a Node-B 104 and a radio network controller (RNC) 106. The RNC 106 controls overall E-DCH operation by configuring E-DCH parameters for the Node-B 104 and the WTRU 102, such as initial transmit power level, maximum allowed transmit power or available channel resources per Node-B. Between the WTRU 102 and the Node-B 104, an E-DCH 108, an E-DCH dedicated physical control channel (E-DPCCH), an E-DCH absolute grant channel (E-AGCH) 112, an E-RGCH 114 and an E-DCH hybrid automatic repeat request (H-ARQ) indicator channel (E-HICH) 116 are established for supporting E-DCH operations.
For E-DCH transmissions, the WTRU 102 sends scheduling requests, (also known as rate requests), for the logical channels which a radio resource control (RRC) determines that reporting is needed to be made to the Node-B 104 via the E-DCH 108. The scheduling requests are transmitted in the form of scheduling information and a happy bit. The happy bit is transmitted via the E-DPCCH 110 whenever the E-DPCCH 110 is transmitted. The Node-B 104 sends a scheduling grant to the WTRU 102 via the E-AGCH 112 or the E-RGCH 114. The scheduling grant is one of absolute grant and a relative grant. The absolute grant is sent by an E-DCH serving radio link set (RLS) via the E-AGCH 112, and the relative grant is sent by either the E-DCH serving RLS or an E-DCH non-serving radio link (RL) via the E-RGCH 114. After E-DCH radio resources are allocated for the WTRU 102, the WTRU 102 transmits uplink data via the E-DCH 108. In response to E-DCH or E-DPCCH transmissions, the Node-B 104 sends an acknowledgement (ACK) or a non-acknowledgement (NACK) message for H-ARQ operation via the E-HICH 116.
The E-AGCH 112 carries the absolute grant in the form of a maximum power ratio for the WTRU 102. The maximum power ratio is given by the ratio of enhanced uplink dedicated physical data channel (E-DPDCH) over dedicated physical control channel (DPCCH) power. The E-RGCH 114 carries the relative grant. The relative grant indicates power (or power ratio) up or down commands to adjust the absolute grant. The E-DCH serving RLS may send UP, DOWN or HOLD commands. The E-DCH non-serving RL may send UP or HOLD commands. The UP, DOWN or HOLD commands indicate an increase, decrease or no change of the maximum allowed power ratio of the WTRU 102 for the scheduled transmission of data, respectively. The commands from different non-serving RLs may be different from one another. The E-DCH non-serving RLs send the relative grant to prevent system overloading in data traffic and maintain the intra-cell and inter-cell interference at the required level.
The successful detection and decoding of the E-RGCH 114 is important for the performance of systems and the performance of enhanced uplink. Therefore, it is desirable to have a method and apparatus for efficiently detecting and decoding E-RGCH signals.